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Stacey Crescitelli is parenting her third teenager after successfully steering daughters Anna, 19, and Sophia, 18, to adulthood. So when her third child, Henry, now 14, began growing at at a fast pace, sleeping more and thinning out, she and her husband Joe thought he was just being a typical teen. As it turns out, his body was actually fighting something more sinister than teenage hormones: Type 1 diabetes.

Now, Crescitelli wants other parents of teenagers to know about the symptoms of Type 1 diabetes. But how can parents tell the difference between what is normal and what is not when it comes to teens?

Joe and Stacey Crescitelli with their children Anna, Sophia, Henry, and Grace.Stacey Crescitelli

Crescitelli, 46, noticed that since December, Henry had grown a lot, "maybe four or five inches," she told TODAY Parents, "and his body was changing. He has always been kind of a solid boy with a large frame — never one of those reed thin, gangly boys — but suddenly, he was becoming one," she said, "and of course, we thought he was simply 'leaning out,'" she said.

Though Henry continued to lose weight and began to sleep more, it was not until this past March that the Doylestown, Pennsylvania, mother noticed symptoms that did not fit with what she believed was normal for teenage boys. That was when Henry suffered from a sudden bout of vertigo that "terrified him and mystified us," said Crescitelli.

"One minute he was in the kitchen getting water, and the next he was asking me to help him to the couch because he couldn't walk or focus his eyes," she said. The vertigo lasted for a day, but it was the beginning of more new symptoms: frequent, though not daily, headaches, dizziness, and stomachaches. Then, Henry began to complain that his legs ached. "We assured him that this was normal when someone was growing rapidly and that he could try to stretch and maybe not sleep with the giant family dog so he could have more room at night," said Crescitelli.

Finally, with his weight loss reaching 25 pounds and his sleep increasing more and more, the Crescitellis realized something was definitely off with their son. "My husband and I suspected maybe he was depressed, until one night Joe just looked at me and we both kind of knew that something now was very wrong," said Crescitelli. They called their nurse practitioner, Pat Chicon, and took Henry in for blood work and a urine test.

Henry was diagnosed with Type 1 diabetes, and by the time he was diagnosed, he was in full-blown diabetic ketoacidosis and had to be hospitalized at the Children's Hospital of Pennsylvania for four days until he was stabilized.

Henry Crescitelli, now 14, grew taller and lost about 25 pounds before his symptoms stood out to his parents as more than a teen growth spurt.Stacey Crescitelli

Type 1 diabetes, an autoimmune disease that causes the body’s immune system to attack and destroy the insulin-producing cells in the pancreas, affects about 208,000 Americans under the age of 20. "It can be tough to recognize signs and symptoms of Type I diabetes in a teen," acknowledged Dr. Nirali Patel, a pediatric emergency medicine physician at Akron Children's Hospital in Ohio.

Dr. Patel said the symptoms of Type 1 diabetes usually include some of the symptoms the Crescitellis saw in Henry, including weight loss and increased fatigue, nausea and abdominal pain, and blurry vision. But symptoms also usually include increased thirst and hunger, increased urination, and signs of dehydration, like cracked lips, sunken eyes, and pale skin. "Since Henry is a teen, I wasn't tracking his urination or thirst," said Crescitelli.

Crescitelli said she didn't realize that even though children grow taller sometimes quickly as teenagers, they should not lose weight during growth spurts. Henry's other symptoms were only significant once they became part of a pattern.

"Recognition is especially difficult given that most parents would find [the symptoms for Type 1 diabetes] somewhat typical for today's teen," acknowledges Dr. Patel. "However, it is the appearance of multiple symptoms — symptoms that are out of proportion relative to the teen's baseline behavior or the emergence of new behaviors — that should alert parents that there may be an underlying medical issue."

Patel offered some examples: a child who never used to get up at night to urinate who now needs to get up two or three times a night to use the bathroom; a teen who is usually social or active but starts staying at home more often or withdrawing from usual activities; or a teen with a voracious appetite who is still losing weight, maybe also looking pale or unwell.

"I most certainly never thought about diabetes for one minute" before this spring, said Crescitelli. "In my wildest imagination, I wouldn't have guessed this diagnosis. Know these basic symptoms and look for patterns over time," she said, adding that her son's diagnosis has "changed" her.

"There is grief and anger and lots of anxiety as I manage his days and help him manage this disease," she said. "Henry has always been an easy going and adaptable child, and though I see him struggle in his own quiet ways, I think he often managed it much better than I do."